Lightweight proppant and methods for making and using same

ABSTRACT

Lightweight proppant particles are disclosed. The lightweight proppant particle can include a proppant particle having an apparent specific gravity of at least about 1.5 g/cc, a coating of a hydrophobic material formed on an outer surface of the proppant particle, and a coating of an amphiphilic material formed on an outer surface of the coating of the hydrophobic material.

FIELD

Embodiments of the present invention relate generally to hydraulicfracturing of geological formations, and more particularly to proppantsused in the hydraulic fracture stimulation of oil and gas reservoirs.

BACKGROUND

In order to stimulate and more effectively produce hydrocarbons fromdownhole formations, especially formations with low porosity and/or lowpermeability, induced fracturing (called “frac operations”, “hydraulicfracturing”, or simply “fracing”) of the hydrocarbon-bearing formationshas been a commonly used technique. In a typical frac operation, fluidsare pumped downhole under high pressure, causing the formations tofracture around the borehole, creating high permeability conduits thatpromote the flow of the hydrocarbons into the borehole. These fracoperations can be conducted in horizontal and deviated, as well asvertical, boreholes, and in either intervals of uncased wells, or incased wells through perforations.

In cased boreholes in vertical wells, for example, the high pressurefluids exit the borehole via perforations through the casing andsurrounding cement, and cause the formations to fracture, usually inthin, generally vertical sheet-like fractures in the deeper formationsin which oil and gas are commonly found. These induced fracturesgenerally extend laterally a considerable distance out from the wellboreinto the surrounding formations, and extend vertically until thefracture reaches a formation that is not easily fractured above and/orbelow the desired frac interval. The directions of maximum and minimumhorizontal stress within the formation determine the azimuthalorientation of the induced fractures. Normally, if the fluid, sometimescalled slurry, pumped downhole does not contain solids that remainlodged in the fracture when the fluid pressure is relaxed, then thefracture re-closes, and most of the permeability conduit gain is lost.

These solids, called proppants, are generally composed of sand grains orceramic particles, and the fluid used to pump these solids downhole isusually designed to be sufficiently viscous such that the proppantparticles remain entrained in the fluid as it moves downhole and outinto the induced fractures. Prior to producing the fractured formations,materials called “breakers” can be pumped downhole in the frac fluidslurry to reduce the viscosity of the frac fluid after a desired timedelay to enable these fluids to be removed from the fractures duringproduction. However, the cross-linked polymers can still accumulate inthe fracture, thereby reducing the permeability of gas or oil throughthe fracture.

There is a need, therefore, for proppant particles that can be entrainedin a fracturing fluid without the need for viscous cross-linked polymersthat can accumulate in the fracture.

DETAILED DESCRIPTION

In the following description, numerous specific details are set forth.However, it is understood that embodiments of the invention may bepracticed without these specific details. In other instances, well-knownstructures and techniques have not been shown in detail in order not toobscure the understanding of this description.

Described herein are proppant compositions having hydrophobicproperties. In particular, proppant particles containing a hydrophobicmaterial are described herein. Also described herein are methods formaking proppant having hydrophobic and hydrophilic properties. Inparticular, methods of infusing a hydrophobic material into an internalporosity of the proppant particles are described herein. Also describedherein are methods of using proppant compositions having hydrophobicproperties. In particular, methods of hydraulic fracturing,frac-packing, and/or gravel packing with proppant particles containing ahydrophobic material are described herein.

The proppant compositions disclosed herein can be or include lightweightproppant. The lightweight proppant can have a hydrophobic component. Inone or more exemplary embodiments, the lightweight proppant can have ahydrophobic component and an amphiphilic component. For example, thelightweight proppant can include a proppant particle treated with ahydrophobic material and having one or more coatings of an amphiphilicmaterial on an outer surface thereof.

In one or more exemplary embodiments, the proppant particle has aninternal porosity that is at least partially infused with thehydrophobic material. For example, the internal porous structure of theproppant particle can be at least partially treated with the hydrophobicmaterial and the outer surface of the proppant particle can be at leastpartially coated with the amphiphilic material. In one or more exemplaryembodiments, the hydrophobic treatment and the amphiphilic coating areboth fluid permeable. In one or more exemplary embodiments, thehydrophobic treatment and the amphiphilic coating do not trap air withinthe porous structure of the proppant particle. The hydrophobic treatmentcan be or include any modification of a surface tension of the proppantwith water that results in decreasing a surface energy of one or moreceramic channels of the internal porous structure of the proppantparticle, resulting in repelling of water from the channels.

In one or more exemplary embodiments, the hydrophobic material can be orinclude any suitable material having hydrophobic properties. Thehydrophobic material can be or include any silicon containing compound,including silicone materials, silanes, and siloxanes, fluorinatedorganic compounds, polytetrafluoroethylene (commonly known as Teflon™),plant oils, such as linseed oil, soybean oil, corn oil, cottonseed oil,vegetable oil (widely commercially available such as Crisco®), andcanola oil, hydrocarbons, such as kerosene, diesel, and crude oil,petroleum distillates, such as hydrocarbon liquids comprising a mixtureof C₇-C₁₂ aliphatic and alicyclic hydrocarbons and aromatic hydrocarbons(C₇-C₁₂), commonly known as Stoddard Solvent, aliphatic solvents,solvent naphtha (medium aliphatic and light aromatic), and paraffin,such as solvent dewaxed heavy paraffinic petroleum distillate andstearates, such as calcium stearate. The hydrophobic material can alsobe or include any one or more polymers or copolymers of acrylates,meth(acrylates), urethanes, epoxies, amides, imides, esters, one or moreethers, olefins, fluorocarbons, and styrenic monomers. The one or morepolymers or copolymers can be or include any suitable fluorinatedpolymers or copolymers. In one or more exemplary embodiments, thehydrophobic material can be or include one or more poly dialkylsiloxanes, such as polydimethylsiloxane (PDMS), one or moreorganosilanes, such as tetraalkoxysilane and trialkoxysilane, one ormore fluorinated siloxanes, one or more fluorinated urethanes, and oneor more fluorinated silanes. In one or more exemplary embodiments, thehydrophobic material is PDMS. The PDMS can include modified PDMS, suchas minopropyl terminated PDMS, hydroxyl terminated PDMS, acrylateterminated PDMS, methacylate terminated PDMS, silanol terminated PDMS,silane terminated PDMS, and vinyl terminated PDMS.

The hydrophobic material can have any suitable degree of hydrophobicity(water repellency). In one or more exemplary embodiments, the outersurface of the hydrophobic material has a hydrophobicity value asmeasured by a water droplet contact angle of at least about 90°, atleast about 100°, at least about 110°, at least about 120°, at leastabout 130°, or at least about 150°.

The lightweight proppant can include any suitable concentration ofhydrophobic material. In one or more exemplary embodiments, thelightweight proppant has a hydrophobic material concentration of atleast about 0.01 wt %, at least about 0.05 wt %, at least about 0.1 wt%, at least about 0.25 wt %, at least about 0.5 wt %, at least about0.75 wt %, or at least about 1 wt %, based on the weight of thelightweight proppant particle. In one or more exemplary embodiments, thelightweight proppant has a hydrophobic material concentration of lessthan 5 wt %, less than 3 wt %, less than 2 wt %, less than 1.5 wt %, orless than 1 wt %, based on the weight of the lightweight proppantparticle. The lightweight proppant can have a hydrophobic materialconcentration from about 0.02 wt %, about 0.08 wt %, about 0.15 wt %,about 0.3 wt %, or about 0.6 wt % to about 0.7 wt %, about 0.8 wt %,about 0.9 wt %, about 1 wt %, about 1.25 wt %, about 1.5 wt %, or about2 wt % or more based on the weight of the lightweight proppant particle.

According to several exemplary embodiments, the amphiphilic coating canbe or include any one or more resin materials, epoxy resin materials,waxes, polyolefins, poly(lactic acids), styrenic polymers, or otherpolymeric materials. According to several exemplary embodiments, theresin material includes any suitable resin capable of being coated ontoa proppant particle. For example, the resin material can include aphenolic resin, such as a phenol-formaldehyde resin.

According to several exemplary embodiments, the phenol-formaldehyderesin has a molar ratio of formaldehyde to phenol (F:P) from a low ofabout 0.6:1, about 0.9:1, or about 1.2:1 to a high of about 1.9:1, about2.1:1, about 2.3:1, or about 2.8:1. For example, the phenol-formaldehyderesin can have a molar ratio of formaldehyde to phenol of about 0.7:1 toabout 2.7:1, about 0.8:1 to about 2.5:1, about 1:1 to about 2.4:1, about1.1:1 to about 2.6:1, or about 1.3:1 to about 2:1. Thephenol-formaldehyde resin can also have a molar ratio of formaldehyde tophenol of about 0.8:1 to about 0.9:1, about 0.9:1 to about 1:1, about1:1 to about 1.1:1, about 1.1:1 to about 1.2:1, about 1.2:1 to about1.3:1, or about 1.3:1 to about 1.4:1.

According to several exemplary embodiments, the phenol-formaldehyderesin has a molar ratio of less than 1:1, less than 0.9:1, less than0.8:1, less than 0.7:1, less than 0.6:1, or less than 0.5:1. Forexample, the phenol-formaldehyde resin can be or include a phenolicnovolac resin. Phenolic novolac resins are well known to those ofordinary skill in the art, for instance see U.S. Pat. No. 2,675,335 toRankin, U.S. Pat. No. 4,179,429 to Hanauye, U.S. Pat. No. 5,218,038 toJohnson, and U.S. Pat. No. 8,399,597 to Pullichola, the entiredisclosures of which are incorporated herein by reference. Suitableexamples of commercially available novolac resins include novolac resinsavailable from Plenco™, Durite® resins available from Momentive, andnovolac resins available from S.I. Group.

According to several exemplary embodiments, the phenol-formaldehyderesin has a weight average molecular weight from a low of about 200,about 300, or about 400 to a high of about 1,000, about 2,000, or about6,000. For example, the phenol-formaldehyde resin can have a weightaverage molecular weight from about 250 to about 450, about 450 to about550, about 550 to about 950, about 950 to about 1,500, about 1,500 toabout 3,500, or about 3,500 to about 6,000. The phenol-formaldehyderesin can also have a weight average molecular weight of about 175 toabout 800, about 700 to about 3,330, about 1,100 to about 4,200, about230 to about 550, about 425 to about 875, or about 2,750 to about 4,500.

According to several exemplary embodiments, the phenol-formaldehyderesin has a number average molecular weight from a low of about 200,about 300, or about 400 to a high of about 1,000, about 2,000, or about6,000. For example, the phenol-formaldehyde resin can have a numberaverage molecular weight from about 250 to about 450, about 450 to about550, about 550 to about 950, about 950 to about 1,500, about 1,500 toabout 3,500, or about 3,500 to about 6,000. The phenol-formaldehyderesin can also have a number average molecular weight of about 175 toabout 800, about 700 to about 3,000, about 1,100 to about 2,200, about230 to about 550, about 425 to about 875, or about 2,000 to about 2,750.

According to several exemplary embodiments, the phenol-formaldehyderesin has a z-average molecular weight from a low of about 200, about300, or about 400 to a high of about 1,000, about 2,000, or about 9,000.For example, the phenol-formaldehyde resin can have a z-averagemolecular weight from about 250 to about 450, about 450 to about 550,about 550 to about 950, about 950 to about 1,500, about 1,500 to about3,500, about 3,500 to about 6,500, or about 6,500 to about 9,000. Thephenol-formaldehyde resin can also have a z-average molecular weight ofabout 175 to about 800, about 700 to about 3,330, about 1,100 to about4,200, about 230 to about 550, about 425 to about 875, or about 4,750 toabout 8,500.

According to several exemplary embodiments, the phenol-formaldehyderesin has any suitable viscosity. The phenol-formaldehyde resin can be asolid or liquid at 25° C. For example, the viscosity of thephenol-formaldehyde resin can be from about 1 centipoise (cP), about 100cP, about 250 cP, about 500 cP, or about 700 cP to about 1,000 cP, about1,250 cP, about 1,500 cP, about 2,000 cP, or about 2,200 cP at atemperature of about 25° C. In another example, the phenol-formaldehyderesin can have a viscosity from about 1 cP to about 125 cP, about 125 cPto about 275 cP, about 275 cP to about 525 cP, about 525 cP to about 725cP, about 725 cP to about 1,100 cP, about 1,100 cP to about 1,600 cP,about 1,600 cP to about 1,900 cP, or about 1,900 cP to about 2,200 cP ata temperature of about 25° C. In another example, thephenol-formaldehyde resin can have a viscosity from about 1 cP to about45 cP, about 45 cP to about 125, about 125 cP to about 550 cP, about 550cP to about 825 cP, about 825 cP to about 1,100 cP, about 1,100 cP toabout 1,600 cP, or about 1,600 cP to about 2,200 cP at a temperature ofabout 25° C. The viscosity of the phenol-formaldehyde resin can also befrom about 500 cP, about 1,000 cP, about 2,500 cP, about 5,000 cP, orabout 7,500 cP to about 10,000 cP, about 15,000 cP, about 20,000 cP,about 30,000 cP, or about 75,000 cP at a temperature of about 150° C.For example, the phenol-formaldehyde resin can have a viscosity fromabout 750 cP to about 60,000 cP, about 1,000 cP to about 35,000 cP,about 4,000 cP to about 25,000 cP, about 8,000 cP to about 16,000 cP, orabout 10,000 cP to about 12,000 cP at a temperature of about 150° C. Theviscosity of the phenol-formaldehyde resin can be determined using aBrookfield viscometer.

According to several exemplary embodiments, the phenol-formaldehyderesin can have pH from a low of about 1, about 2, about 3, about 4,about 5, about 6, about 7 to a high of about 8, about 9, about 10, about11, about 12, or about 13. For example, the phenol-formaldehyde resincan have a pH from about 1 to about 2.5, about 2.5 to about 3.5, about3.5 to about 4.5, about 4.5 to about 5.5, about 5.5 to about 6.5, about6.5 to about 7.5, about 7.5 to about 8.5, about 8.5 to about 9.5, about9.5 to about 10.5, about 10.5 to about 11.5, about 11.5 to about 12.5,or about 12.5 to about 13.

According to several exemplary embodiments of the present invention, theamphiphilic coating applied to the proppant particles is an epoxy resin.According to such embodiments, the amphiphilic coating can be or includeany suitable epoxy resin. For example, the epoxy resin can includebisphenol A, bisphenol F, aliphatic, or glycidylamine epoxy resins, andany mixtures or combinations thereof. An example of a commerciallyavailable epoxy resin is BE188 Epoxy Resin, available from Chang ChunPlastics Co., Ltd.

According to several exemplary embodiments, the epoxy resin can have anysuitable viscosity. The epoxy resin can be a solid or liquid at 25° C.For example, the viscosity of the epoxy resin can be from about 1 cP,about 100 cP, about 250 cP, about 500 cP, or about 700 cP to about 1,000cP, about 1,250 cP, about 1,500 cP, about 2,000 cP, or about 2,200 cP ata temperature of about 25° C. In another example, the epoxy resin canhave a viscosity from about 1 cP to about 125 cP, about 125 cP to about275 cP, about 275 cP to about 525 cP, about 525 cP to about 725 cP,about 725 cP to about 1,100 cP, about 1,100 cP to about 1,600 cP, about1,600 cP to about 1,900 cP, or about 1,900 cP to about 2,200 cP at atemperature of about 25° C. In another example, the epoxy resin can havea viscosity from about 1 cP to about 45 cP, about 45 cP to about 125 cP,about 125 cP to about 550 cP, about 550 cP to about 825 cP, about 825 cPto about 1,100 cP, about 1,100 cP to about 1,600 cP, or about 1,600 cPto about 2,200 cP at a temperature of about 25° C. The viscosity of theepoxy resin can also be from about 500 cP, about 1,000 cP, about 2,500cP, about 5,000 cP, or about 7,000 cP to about 10,000 cP, about 12,500cP, about 15,000 cP, about 17,000 cP, or about 20,000 cP at atemperature of about 25° C. In another example, the epoxy resin can havea viscosity from about 1,000 cP to about 12,000 cP, about 2,000 cP toabout 11,000 cP, about 4,000 cP to about 10,500 cP, or about 7,500 cP toabout 9,500 cP at a temperature of about 25° C. The viscosity of theepoxy resin can also be from about 500 cP, about 1,000 cP, about 2,500cP, about 5,000 cP, or about 7,500 cP to about 10,000 cP, about 15,000cP, about 20,000 cP, about 30,000 cP, or about 75,000 cP at atemperature of about 150° C. For example, the epoxy resin can have aviscosity from about 750 cP to about 60,000 cP, about 1,000 cP to about35,000 cP, about 4,000 cP to about 25,000 cP, about 8,000 cP to about16,000 cP, or about 10,000 cP to about 12,000 cP at a temperature ofabout 150° C.

According to several exemplary embodiments, the epoxy resin can have pHfrom a low of about 1, about 2, about 3, about 4, about 5, about 6,about 7 to a high of about 8, about 9, about 10, about 11, about 12, orabout 13. For example, the epoxy resin can have a pH from about 1 toabout 2.5, about 2.5 to about 3.5, about 3.5 to about 4.5, about 4.5 toabout 5.5, about 5.5 to about 6.5, about 6.5 to about 7.5, about 7.5 toabout 8.5, about 8.5 to about 9.5, about 9.5 to about 10.5, about 10.5to about 11.5, about 11.5 to about 12.5, or about 12.5 to about 13.

According to several exemplary embodiments, the amphiphilic coating canbe or include any one or more wetting agents. According to severalexemplary embodiments, the wetting agent is capable of being coated ontoa proppant particle. Specific examples of wetting agents can include,but are not limited to, alkyl sulfonates, alkyl aryl sulfonatesincluding alkyl benzyl sulfonates such as salts of dodecylbenzenesulfonic acid, alkyl trimethylammonium chloride, branched alkylethoxylated alcohols, phenol-formaldehyde nonionic resin blends,cocobetaines, dioctyl sodium sulfosuccinate, imidazolines, alpha olefinsulfonates, linear alkyl ethoxylated alcohols, trialkyl benzylammoniumchloride, polyaminated fatty acids, and the like. In one or moreexemplary embodiments, the wetting agent can be or includecocoamidopropyl hydroxysultaine, cocoamidopropyl betaine, ethoxylatedlauryl alcohol, ethoxylated tridecyl alcohol, ethoxylated C9-C11alcohols, ethoxylated C11-C13 alcohols, polyethylene glycol,laurylamidopropyl betaine, Dioctosulfosuccinate, alkoxylated linearalcohol, ethoxylated castor oil, polysorbate, or glycerol monolaurate orany combination thereof.

The amphiphilic material can have any suitable degree of waterwettability and/or oil wettability. In one or more exemplaryembodiments, the outer surface of the amphiphilic material has a waterwettability value as measured by a water droplet contact angle of lessthan 90°, less than 80°, less than 70°, less than 60°, less than 50°, orabout 45° or less. In one or more exemplary embodiments, the outersurface of the amphiphilic material has an oil wettability value asmeasured by an oil droplet contact angle of less than 90°, less than80°, less than 70°, less than 60°, less than 50°, or about 45° or less.

The lightweight proppant can include any suitable concentration of theamphiphilic material. In one or more exemplary embodiments, thelightweight proppant has an amphiphilic material concentration of atleast about 0.05 wt %, at least about 0.1 wt %, at least about 0.5 wt %,at least about 1 wt %, at least about 1.5 wt %, at least about 2 wt %,or at least about 2.5 wt %, based on the weight of the lightweightproppant particle. In one or more exemplary embodiments, the lightweightproppant has a hydrophobic material concentration of less than 10 wt %,less than 8 wt %, less than 6 wt %, less than 4 wt %, or less than 3 wt%, based on the weight of the lightweight proppant particle. Thelightweight proppant can have an amphiphilic material concentration fromabout 0.08 wt %, about 0.12 wt %, about 0.25 wt %, about 0.75 wt %,about 1.25 wt %, or about 1.75 wt % to about 2 wt %, about 2.25 wt %,about 2.5 wt %, about 2.75 wt %, about 3 wt %, about 3.5 wt %, or about5 wt % or more based on the weight of the lightweight proppant particle.

The proppant particle can be selected from the group of ceramicproppant, sand, plastic beads and glass beads. In one or more exemplaryembodiments, the proppant particle can be or include natural sand. Inone or more exemplary embodiments, the proppant particle can be orinclude ceramic proppant. The ceramic proppant can be or include porousceramic proppant and non-porous ceramic proppant. Such proppantparticulates can be manufactured according to any suitable processincluding, but not limited to continuous spray atomization, sprayfluidization, drip casting, spray drying, or compression. Suitableproppant particulates and methods for manufacture are disclosed in U.S.Pat. Nos. 4,068,718, 4,427,068, 4,440,866, 5,188,175, 7,036,591,8,865,631, 8,883,693, and 9,175,210, and U.S. patent application Ser.Nos. 14/502,483 and 14/802,761, the entire disclosures of which areincorporated herein by reference, the entire disclosures of which areincorporated herein by reference.

The proppant particle can be or include silica and/or alumina in anysuitable amounts. According to several exemplary embodiments, theproppant particle includes less than 80 wt %, less than 60 wt %, lessthan 40 wt %, less than 30 wt %, less than 20 wt %, less than 10 wt %,or less than 5 wt % silica based on the total weight of the proppantparticle. According to several exemplary embodiments, the proppantparticle includes from about 0.1 wt % to about 70 wt % silica, fromabout 1 wt % to about 60 wt % silica, from about 2.5 wt % to about 50 wt% silica, from about 5 wt % to about 40 wt % silica, or from about 10 wt% to about 30 wt % silica. According to several exemplary embodiments,the proppant particle includes at least about 30 wt %, at least about 50wt %, at least about 60 wt %, at least about 70 wt %, at least about 80wt %, at least about 90 wt %, or at least about 95 wt % alumina based onthe total weight of the proppant particle. According to severalexemplary embodiments, the proppant particle includes from about 30 wt %to about 99.9 wt % alumina, from about 40 wt % to about 99 wt % alumina,from about 50 wt % to about 97 wt % alumina, from about 60 wt % to about95 wt % alumina, or from about 70 wt % to about 90 wt % alumina.

According to several exemplary embodiments, the proppant compositionsdisclosed herein include proppant particles that are substantially roundand spherical having a size in a range between about 6 and 270 U.S.Mesh. For example, the size of the proppant particle can be expressed asa grain fineness number (GFN) in a range of from about 15 to about 300,or from about 30 to about 110, or from about 40 to about 70. Accordingto such examples, a sample of proppant particles can be screened in alaboratory for separation by size, for example, intermediate sizesbetween 20, 30, 40, 50, 70, 100, 140, 200, and 270 U.S. mesh sizes todetermine GFN. The correlation between sieve size and GFN can bedetermined according to Procedure 106-87-S of the American FoundrySociety Mold and Core Test Handbook, which is known to those of ordinaryskill in the art.

The proppant particles can have any suitable size. For example, theproppant particle can have a mesh size of at least about 6 mesh, atleast about 10 mesh, at least about 16 mesh, at least about 20 mesh, atleast about 25 mesh, at least about 30 mesh, at least about 35 mesh, orat least about 40 mesh. According to several exemplary embodiments, theproppant particle has a mesh size from about 6 mesh, about 10 mesh,about 16 mesh, or about 20 mesh to about 25 mesh, about 30 mesh, about35 mesh, about 40 mesh, about 45 mesh, about 50 mesh, about 70 mesh, orabout 100 mesh. According to several exemplary embodiments, the proppantparticle has a mesh size from about 4 mesh to about 120 mesh, from about10 mesh to about 60 mesh, from about 16 mesh to about 20 mesh, fromabout 20 mesh to about 40 mesh, or from about 25 mesh to about 35 mesh.

According to several exemplary embodiments, the proppant compositionsdisclosed herein include porous and/or non-porous proppant particleshaving any suitable permeability and conductivity in accordance with ISO13503-5: “Procedures for Measuring the Long-term Conductivity ofProppants,” and expressed in terms of Darcy units, or Darcies (D). Apack of the proppant particles, having a 20/40 mesh size range, can havea long term permeability at 7,500 psi of at least about 1 D, at leastabout 2 D, at least about 5 D, at least about 10 D, at least about 20 D,at least about 40 D, at least about 80 D, at least about 120 D, at leastabout 150 D, at least about 200 D, or at least about 250 D. The pack ofthe proppant particles, having a 20/40 mesh size range, can have a longterm permeability at 12,000 psi of at least about 1 D, at least about 2D, at least about 3 D, at least about 4 D, at least about 5 D, at leastabout 10 D, at least about 25 D, at least about 50 D, at least about 100D, at least about 150 D, or at least about 200 D. The pack of theproppant particles, having a 20/40 mesh size range, can have a long termpermeability at 15,000 psi of at least about 1 D, at least about 2 D, atleast about 3 D, at least about 4 D, at least about 5 D, at least about10 D, at least about 25 D, at least about 50 D, at least about 75 D, atleast about 100 D, or at least about 150 D. The pack of the proppantparticles, having a 20/40 mesh size range, can have a long termpermeability at 20,000 psi of at least about 1 D, at least about 2 D, atleast about 3 D, at least about 4 D, at least about 5 D, at least about10 D, at least about 25 D, at least about 50 D, at least about 75 D, orat least about 100 D.

A pack of the proppant particles can have a long term conductivity at7,500 psi of at least about 100 millidarcy-feet (mD-ft), at least about200 mD-ft, at least about 300 mD-ft, at least about 500 mD-ft, at leastabout 1,000 mD-ft, at least about 1,500 mD-ft, at least about 2,000mD-ft, or at least about 2,500 mD-ft. For example, a pack of theproppant particles can have a long term conductivity at 12,000 psi of atleast about 50 mD-ft, at least about 100 mD-ft, at least about 200mD-ft, at least about 300 mD-ft, at least about 500 mD-ft, at leastabout 1,000 mD-ft, or at least about 1,500 mD-ft.

The proppant compositions disclosed herein include proppant particleshaving any suitable shape. The proppant particles can be substantiallyround, cylindrical, square, rectangular, elliptical, oval, egg-shaped,or pill-shaped. In one or more exemplary embodiments, the proppantparticles are substantially round and spherical.

The proppant particles can have any suitable apparent specific gravity.As used herein, the term “apparent specific gravity” refers to theweight per unit volume (grams per cubic centimeter) of an object,wherein the volume of the object is the volume of water displaced bysubmerging the object in water. The proppant particles can have anapparent specific gravity of at least about 1.5 g/cc, at least about 1.7g/cc, at least about 1.9 g/cc, at least about 2.1 g/cc, at least about2.3 g/cc, at least about 2.5 g/cc, at least about 2.7 g/cc, at leastabout 3 g/cc, at least about 3.3 g/cc, or at least about 3.5 g/cc. Inone or more exemplary embodiments, the proppant particles can have anapparent specific gravity of less than 4 g/cc, less than 3.5 g/cc, lessthan 3 g/cc, less than 2.75 g/cc, less than 2.5 g/cc, or less than 2.25g/cc. For example, the proppant particles can have an apparent specificgravity of about 1.6 g/cc to about 3.5 g/cc, about 1.8 g/cc to about 3.2g/cc, about 2.0 g/cc to about 2.7 g/cc, about 2.1 g/cc to about 2.4g/cc, or about 2.2 g/cc to about 2.6 g/cc.

The proppant particles can have any suitable bulk density. As usedherein, the term “bulk density” refers to the weight per unit volume(grams per cubic centimeter) of a plurality of objects including thevoid spaces between the particles in the volume considered. In one ormore exemplary embodiments, the proppant particles have a bulk densityof less than 3 g/cc, less than 2.5 g/cc, less than 2.2 g/cc, less than 2g/cc, less than 1.8 g/cc, less than 1.6 g/cc, or less than 1.5 g/cc. Theproppant particles can have a bulk density of about 1 g/cc, about 1.15g/cc, about 1.25 g/cc, about 1.35 g/cc, or about 1.45 g/cc to about 1.5g/cc, about 1.6 g/cc, about 1.75 g/cc, about 1.9 g/cc, or about 2.1 g/ccor more. For example, the proppant particles can have a bulk density ofabout 1.3 g/cc to about 1.8 g/cc, about 1.35 g/cc to about 1.65 g/cc, orabout 1.5 g/cc to about 1.9 g/cc.

The proppant particles can have any suitable surface roughness. Theproppant particles can have a surface roughness of less than 5 μm, lessthan 4 μm, less than 3 μm, less than 2.5 μm, less than 2 μm, less than1.5 μm, or less than 1 μm. For example, the proppant particles can havea surface roughness of about 0.1 μm to about 4.5 μm, about 0.4 μm toabout 3.5 μm, or about 0.8 μm to about 2.8 μm.

The proppant particles can have any suitable porosity. According toseveral exemplary embodiments, the proppant particles can be or includeporous ceramic proppant having any suitable porosity. The porous ceramicproppant can have an internal interconnected porosity from about 1%,about 2%, about 4%, about 6%, about 8%, about 10%, about 12%, or about14% to about 18%, about 20%, about 22%, about 24%, about 26%, about 28%,about 30%, about 34%, about 38%, about 45%, about 55%, about 65%, orabout 75% or more. In several exemplary embodiments, the internalinterconnected porosity of the porous ceramic proppant is from about 5%to about 75%, about 5% to about 15%, about 10% to about 30%, about 15%to about 35%, about 25% to about 45%, about 30% to about 55%, or about35% to about 70%. According to several exemplary embodiments, the porousceramic proppant can have any suitable average pore size. For example,the porous ceramic proppant can have an average pore size from about 2nm, about 10 nm, about 15 nm, about 55 nm, about 110 nm, about 520 nm,or about 1,100 to about 2,200 nm, about 5,500 nm, about 11,000 nm, about17,000 nm, or about 25,000 nm or more in its largest dimension. Forexample, the porous ceramic proppant can have an average pore size canbe from about 3 nm to about 30,000 nm, about 30 nm to about 18,000 nm,about 200 nm to about 9,000, about 350 nm to about 4,500 nm, or about850 nm to about 1,800 nm in its largest dimension.

The hydrophobic material can be added to the proppant particulate in anysuitable manner. In one or more exemplary embodiments, the proppantparticulate can be treated with the hydrophobic material by coating thehydrophobic material on at least a portion of the outer surface of theproppant particulate. The hydrophobic material can cover at least about10%, at least about 20%, at least about 35%, at least about 50%, atleast about 65%, at least about 75%, at least about 85%, or at leastabout 95% of the outer surfaces of the proppant particle. Thehydrophobic material can cover, for example, 100% of the outer surfacesof the proppant particle.

In one or more exemplary embodiments, the hydrophobic material can coverless than 100%, less than 99%, less than 95%, less than 90%, less than85%, less than 80%, less than 75%, less than 65%, less than 50%, lessthan 40%, or less than 35% of the outer surfaces of the proppantparticle. In one or more exemplary embodiments, about 25%, about 30%,about 35%, or about 45% to about 55%, about 65%, about 75%, about 85%,about 90%, about 95%, or about 99% or more of the outer surface of theproppant particle can be covered by the hydrophobic material. Forexample, the hydrophobic material can cover from about 10% to about 99%,from about 15% to about 95%, from about 20% to about 75%, from about 25%to about 65%, from about 30% to about 45%, from about 35% to about 75%,from about 45% to about 90%, or from about 40% to about 95% of the outersurface of the proppant particle.

In one or more exemplary embodiments, the proppant particulate can betreated with the hydrophobic material by infusing the hydrophobicmaterial into one or more pores and/or one or more channels of theproppant particulate. In one or more exemplary embodiments, the proppantparticulate can be treated with the hydrophobic material by coating thehydrophobic material onto the one or more pores and/or one or morechannels of the proppant particulate. For example, the hydrophobicmaterial can be applied as a coating on the walls of pores and channelscontained in the internal porous structure, also referred to herein as“pore walls.”

In one or more exemplary embodiments, the coating of the hydrophobicmaterial can cover at least 0.1%, at least about 1%, at least about 2%,at least about 5%, at least about 7%, at least at least about 10%, atleast about 20%, at least about 35%, at least about 50%, at least about65%, at least about 75%, at least about 85%, or at least about 95% ofthe outer surfaces of the pore walls. The hydrophobic material cancover, for example, 100% of the outer surfaces of the pore walls of theproppant particle.

In one or more exemplary embodiments, the coating of the hydrophobicmaterial can cover less than 100%, less than 99%, less than 95%, lessthan 90%, less than 85%, less than 80%, less than 75%, less than 65%,less than 50%, less than 40%, or less than 35% of the outer surfaces ofthe pore walls. In one or more exemplary embodiments, about 25%, about30%, about 35%, or about 45% to about 55%, about 65%, about 75%, about85%, about 90%, about 95%, or about 99% or more of the outer surface ofthe pore walls can be covered by the hydrophobic material. For example,the coating of hydrophobic material can cover from about 10% to about99%, from about 15% to about 95%, from about 20% to about 75%, fromabout 25% to about 65%, from about 30% to about 45%, from about 35% toabout 75%, from about 45% to about 90%, or from about 40% to about 95%of the outer surface of the pore walls.

In one or more exemplary embodiments, at least a portion of pores and/orchannels of the internal porous structure of the proppant particulatelocated at or near the surface of the proppant particulate can be coatedwith the hydrophobic material. For example, the coating of thehydrophobic material can cover at least 10%, at least about 20%, atleast about 30%, at least about 50%, at least about 70%, at least about90%, or at least about 95% of the outer surfaces of the pore wallslocated at or near the surface of the proppant particulate. In one ormore exemplary embodiments, the coating of the hydrophobic materialcovers at least 10%, at least about 20%, at least about 30%, at leastabout 50%, at least about 70%, at least about 90%, or at least about 95%of the outer surfaces of the pore walls located at or near the surfaceof the proppant particulate and less than 50%, less than 30%, less than20%, less than 15%, less than 10%, less than 5%, or less than 1% of thepore walls not located at or near the surface of the proppantparticulate. In one or more exemplary embodiments, only the pores and/orchannels of the internal porous structure of the proppant particulatelocated at or near the surface of the proppant particulate are coatedwith the hydrophobic material.

The hydrophobic coating can have any suitable thickness. In one or moreexemplary embodiments, the hydrophobic coating has an average thicknessranging from about 1 nm, about 5 nm, about 10 nm, about 25 nm, about 50nm, about 100 nm, or about 200 nm to about 300 nm, about 400 nm, about500 nm, about 750 nm, about 1,000 nm, or about 5,000 nm or more. Forexample, the average thickness of the hydrophobic coating can be lessthan 1,000 nm, less than 500 nm, less than 300 nm, less than 250 nm,less than 200 nm, or less than 100 nm.

The proppant particle having the hydrophobic material, or hydrophobicproppant, can be coated with the amphiphilic material to provide thelightweight proppant. For example, the lightweight proppant can have ahydrophobic layer disposed between the amphiphilic material and theproppant particle. The coating of the amphiphilic material can cover atleast about 10%, at least about 15%, at least about 20%, at least about30%, at least about 40%, or at least about 50% of the outer surfaces ofthe hydrophobic proppant particle. In one or more exemplary embodiments,the coating of the amphiphilic material can cover less than 100%, lessthan 99%, less than 95%, less than 90%, less than 85%, less than 80%,less than 75%, less than 65%, less than 50%, less than 40%, or less than35% of the outer surfaces of the hydrophobic proppant particle. In oneor more exemplary embodiments, about 25%, about 30%, about 35%, or about45% to about 55%, about 65%, about 75%, about 85%, about 90%, about 95%,or about 99% or more of the outer surface of the hydrophobic proppantparticle can be covered by the amphiphilic material. For example, thecoating of amphiphilic material can cover from about 10% to about 99%,from about 15% to about 95%, from about 20% to about 75%, from about 25%to about 65%, from about 30% to about 45%, from about 35% to about 75%,from about 45% to about 90%, or from about 40% to about 95% of the outersurface of the hydrophobic proppant particle.

The amphiphilic coating of the lightweight proppant can have anysuitable thickness. In one or more exemplary embodiments, theamphiphilic coating has an average thickness ranging from about 1 nm,about 5 nm, about 10 nm, about 25 nm, about 50 nm, about 100 nm, about250 nm, about 500 nm, about 1,000 nm, or about 2,000 nm to about 3,000nm, about 4,000 nm, about 5,000 nm, about 7,500 nm, about 10,000 about15,000 nm, about 20,000 nm, or about 30,000 nm or more. For example, theaverage thickness of the amphiphilic coating can be less than 30,000 nm,less than 25,000 nm, less than 20,000 nm, less than 15,000 nm, less than10,000 nm, or less than 5,000 nm.

The lightweight proppant can have any suitable bulk density. In one ormore exemplary embodiments, the lightweight proppant can have a bulkdensity of at least about 0.8 g/cc, at least about 1 g/cc, at leastabout 1.5 g/cc, at least about 1.8 g/cc, at least about 2 g/cc, at leastabout 2.2 g/cc, or at least about 2.4 g/cc. The lightweight proppant canhave a bulk density of about 1.15 g/cc, about 1.25 g/cc, about 1.35g/cc, or about 1.45 g/cc to about 1.5 g/cc, about 1.6 g/cc, about 1.75g/cc, about 1.9 g/cc, about 2.1 g/cc, or about 2.5 g/cc or more. Forexample, the lightweight proppant can have a bulk density of about 1.3g/cc to about 1.8 g/cc, about 1.35 g/cc to about 1.65 g/cc, about 1.5g/cc to about 1.9 g/cc, or about 1.6 g/cc to about 2.1 g/cc. In one ormore exemplary embodiments, the lightweight proppant has a bulk densityless than the bulk density of the proppant particle.

The lightweight proppant can have any suitable apparent specificgravity. In one or more exemplary embodiments, the lightweight proppantcan have an apparent specific gravity less than 3 g/cc, less than 2.8g/cc, less than 2.5 g/cc, less than 2.2 g/cc, less than 2 g/cc, lessthan 1.8 g/cc, or less than 1.6 g/cc. The lightweight proppant can havean apparent specific gravity of about 1.25 g/cc, about 1.45 g/cc, about1.65 g/cc, or about 1.85 g/cc to about 1.95 g/cc, about 2 g/cc, about2.1 g/cc, about 2.2 g/cc, or about 2.4 g/cc or more. For example, thelightweight proppant can have an apparent specific gravity of about 1.5g/cc to about 2.5 g/cc, about 1.65 g/cc to about 2.25 g/cc, about 1.4g/cc to about 1.8 g/cc, or about 1.8 g/cc to about 2.1 g/cc. In one ormore exemplary embodiments, the lightweight proppant has an apparentspecific gravity less than the apparent specific gravity of the proppantparticle. The apparent specific gravity of the lightweight proppant canbe less than 95%, less than 90%, less than 85%, less than 80%, less than75%, or less than 70% of the apparent specific gravity of the proppantparticle.

The lightweight proppant can have any suitable degree of waterwettability and/or oil wettability. In one or more exemplaryembodiments, the outer surface of the lightweight proppant has a waterwettability value as measured by a water droplet contact angle of lessthan 90°, less than 80°, less than 70°, less than 60°, less than 50°, orabout 45° or less. In one or more exemplary embodiments, the outersurface of the lightweight proppant has an oil wettability value asmeasured by an oil droplet contact angle of less than 90°, less than80°, less than 70°, less than 60°, less than 50°, or about 45° or less.

The lightweight proppant disclosed herein can be selectively impermeableto aqueous based solutions. In one or more exemplary embodiments, thehydrophobic treatment can prevent water or any other suitable aqueousbased solutions, such as hydraulic fracturing fluids, from enteringand/or saturating the internal porosity of the proppant particles, whilemaintaining open fluid permeability of the internal porosity to gaseouscompositions, such as air. In one or more exemplary embodiments, thehydrophobic treatment can prevent water or any other suitable aqueousbased solutions, such as hydraulic fracturing fluids, from enteringand/or saturating the internal porosity of the proppant particles, whilemaintaining open fluid permeability of the internal porosity to organicphase solutions, such as produced hydrocarbon liquids, and gaseouscompositions, such as air.

The lightweight proppant can be prepared in any suitable manner. Forexample, the lightweight proppant can be prepared by treating bare orraw proppant particles with the hydrophobic material to providehydrophobic proppant particles. In treating the lightweight proppantwith the hydrophobic material, the hydrophobic material can be coatedonto pore walls of the proppant particles. In one or more exemplaryembodiments, hydrophobic material can be coated onto pore walls locatedat or near the proppant surface. The hydrophobic proppant particles canthen be coated with the amphiphilic material to provide the lightweightproppant.

The proppant particles can be treated with the hydrophobic material bycoating the hydrophobic material on and/or infusing the hydrophobicmaterial into the proppant particles in any suitable manner to providethe hydrophobic proppant particles. Suitable methods for treatingproppant particles with hydrophobic material to provide the hydrophobicproppant particles include methods disclosed in U.S. Pat. No. 2,378,817to Wrightsman, U.S. Pat. No. 4,873,145 to Okada and U.S. Pat. No.4,888,240 to Graham, the entire disclosures of which are incorporatedherein by reference. In one or more exemplary embodiments, thehydrophobic material can be coated onto and/or infused into the proppantparticles by mixing the proppant particles with the hydrophobic materialor a solution containing the hydrophobic material. For example, theproppant particles can be submerged into a solution or bath of thehydrophobic material to provide the hydrophobic proppant particles. Inone or more exemplary embodiments, the hydrophobic material can beintroduced into the interstitial or porous spaces of the proppantparticles with systems and methods selected from the group of microwaveblending, vacuum infusion, thermal infusion, capillary action, ribbonblending at room or elevated temperature, and pug mill processing, andany combination thereof.

The amphiphilic material can be coated onto the hydrophobic proppantparticle in any suitable manner. The amphiphilic material can be coatedon the hydrophobic proppant particle in 1, 2, 3, or 4 or more coatingsor coats. Methods for coating proppant particles with resins and/orepoxy resins are well known to those of ordinary skill in the art, forinstance see U.S. Pat. No. 2,378,817 to Wrightsman, U.S. Pat. No.4,873,145 to Okada and U.S. Pat. No. 4,888,240 to Graham, the entiredisclosures of which are incorporated herein by reference.

When used as a proppant, the particles described herein can be handledin the same manner as ordinary proppants. For example, the particles canbe delivered to the well site in bags or in bulk form along with theother materials used in fracturing treatment. Conventional equipment andtechniques can be used to place the particles in the formation as aproppant. For example, the particles are mixed with a fracture fluid,which is then injected into a fracture in the formation.

In an exemplary method of fracturing a subterranean formation, ahydraulic fluid is injected into the formation at a rate and pressuresufficient to open a fracture therein, and a fluid containing thelightweight proppant as described herein and having one or more of theproperties as described herein is injected into the fracture to prop thefracture in an open condition. In an exemplary method of gravel packinga wellbore, a hydraulic fluid containing the lightweight proppant asdescribed herein and having one or more of the properties as describedherein is injected into the a gravel-pack region of a wellbore under arate and pressure suitable for placement of the lightweight proppant asa gravel-pack into the gravel-pack region of the wellbore. In anexemplary method of frac-packing a wellbore, a hydraulic fluidcontaining the lightweight proppant is injected into a frac-pack regionof a wellbore at a rate and pressure sufficient to open a fracture inthe formation extending from and/or adjacent to the frac-pack region ofthe wellbore and under a rate and pressure suitable for placement of thelightweight proppant as a frac-pack into the frac-pack region of thewellbore.

The lightweight proppant can be combined with or admixed with standardor conventional proppant such as bare sand or ceramic proppant. In anexemplary method of fracturing a subterranean formation, a hydraulicfluid is injected into the formation at a rate and pressure sufficientto open a fracture therein, and a fluid containing the lightweight isinjected into the fracture to prop the fracture in an open conditionfollowed by a tail-in injection of a fluid containing conventionalproppant into the fracture. In another exemplary method of fracturing asubterranean formation, a hydraulic fluid is injected into the formationat a rate and pressure sufficient to open a fracture therein, and afluid containing the conventional proppant is injected into the fractureto prop the fracture in an open condition followed by a tail-ininjection of a fluid containing the lightweight proppant. In yet anotherexemplary method of fracturing a subterranean formation, a hydraulicfluid is injected into the formation at a rate and pressure sufficientto open a fracture therein, and a fluid containing a mixture of thelightweight proppant and the conventional proppant is injected into thefracture to prop the fracture in an open condition.

In another exemplary method of gravel packing a wellbore, a hydraulicfluid containing a mixture of the lightweight proppant and theconventional proppant is injected into a gravel-pack region of awellbore under a rate and pressure suitable for placement of thelightweight proppant and/or the conventional proppant as a gravel-packinto the gravel-pack region of the wellbore. In another exemplary methodof frac-packing a wellbore, a hydraulic fluid containing a mixture ofthe lightweight proppant and the conventional proppant is injected intoa frac-pack region of a wellbore at a rate and pressure sufficient toopen a fracture in the formation extending from and/or adjacent to thefrac-pack region of the wellbore and under a rate and pressure suitablefor placement of the lightweight proppant and/or the conventionalproppant as a frac-pack into the frac-pack region of the wellbore.

EXAMPLES

These examples were carried out using exemplary materials in order todetermine apparent specific gravity of lightweight proppant havingvarious coating concentrations of hydrophobic material and amphiphilicmaterial. These examples are meant to be illustrative of exemplaryembodiments of the present invention and are not intended to beexhaustive.

Example 1

A 1000 gram batch (first batch) of 30/50 CARBO UltraLite, anultra-lightweight ceramic proppant having an apparent specific gravityof 2.71 and having a porosity of 20-25% that is commercially availablefrom CARBO Ceramics Inc., was weighed out into a mixing bowl.

The first batch of proppant was heated in an oven set to 482° F. (250°C.) for approximately two hours. The heated first batch of proppant wasthen removed from the oven and allowed to cool until it reached atemperature of between 445-455° F. After the first batch of proppant hadcooled to the process temperature, the proppant was coated with apermeable phenolic coating. The first batch of proppant was coated withthe permeable phenolic coating in a one-step process with a phenolformaldehyde standard reactivity resin that is commercially availablefrom Plastics Engineering Company under the trade name Plenco 14941.

The coating process started with the addition of 16.73 grams of thephenol formaldehyde resin to the proppant and the resin was allowed tomelt and spread over the proppant. Seven seconds after the addition ofthe phenol formaldehyde resin, 0.8 gram of an adhesion promoter,Silquest A1000, which is commercially available from MomentivePerformance Materials, Inc., was added to the batch. Fifteen secondsafter the addition of the phenol formaldehyde resin, 5.44 grams of a 40%hexamethylenetetramine (which is also known as and will be referred toherein as “hexamine”), solution, and which is commercially availablefrom The Chemical Company, was added to crosslink and cure the phenolformaldehyde resin and was allowed to mix for 1 minute 15 seconds.Finally, 1.2 grams of a 50-60% cocoamidopropyl hydroxysultainesurfactant, which is commercially available from The LubrizolCorporation under the trade name “Chembetaine™ CAS”, was added andallowed to mix for 1 minute 30 seconds. After this coating procedure,the first proppant batch included 2.0% by weight of the polymericcoating. The apparent specific gravity for this first batch product was2.52 g/cc.

Example 2

One 750 gram batch (second batch) of 30/50 CARBO UltraLite was weighedout into the mixing bowl. The second batch of proppant was heated in anoven set to 482° F. (250° C.) for approximately two hours. The heatedsecond batch of proppant was then removed from the oven and allowed tocool until it reached a temperature of between 445-455° F. After theproppant particulates had cooled to the process temperature, theproppant was coated with a permeable phenolic coating. The second batchof proppant was coated with the permeable phenolic coating in a one-stepprocess with Plenco 14941.

The coating process started with the addition of 22.8 grams of thephenol formaldehyde resin to the proppant and the resin was allowed tomelt and spread over the proppant. Seven seconds after the addition ofthe phenol formaldehyde resin, 0.8 gram of Silquest A1000 was added tothe batch. Fifteen seconds after the addition of the phenol formaldehyderesin, 7.4 grams of a 40% hexamine solution was added to crosslink andcure the phenol formaldehyde resin and was allowed to mix for 1 minute15 seconds. Finally, 1.2 grams of Chembetaine™ CAS was added and allowedto mix for 1 minute 30 seconds. After the coating procedure, the secondproppant batch included 3.5% by weight of the polymeric coating. Theapparent specific gravity for this second batch product was 2.38 g/cc.

Example 3

One 742.5 gram batch (third batch) of 30/50 CARBO UltraLite was treatedwith a hydrophobic chemical, BYK LPD 22287, having a solids content of100%, which is commercially available from BYK, and was then coated witha permeable phenolic coating in a one-step process as described below.

The third batch of proppant was heated in an oven set to 482° F. (250°C.) for approximately two hours. The heated third batch of proppant wasthen removed from the oven and allowed to cool until it reached atemperature of between 445-455° F. as monitored by a thermocouple. Oncethe third proppant batch reached the desired temperature, 7.5 grams ofBYK LPD 22287 was added to the third batch to bring the batch weight upto 750 g. The BYK LPD 22287 was allowed to coat the inner channels ofthe porous substrate for 20 seconds to provide treated proppant, suchthat the BYK LPD 22287 constituted 1% by weight of the treated proppant.After the proppant particulates were treated with the BYK LPD 22287chemical, the third batch was then coated with a permeable phenoliccoating.

The treated third batch of proppant was coated in a one-step processwith Plenco 14941. Immediately after the proppant batch was treated withthe hydrophobic chemical, 22.82 grams of the phenol formaldehyde resinwas added to the treated proppant and allowed to melt and spread overthe proppant. Seven seconds after the addition of the phenolformaldehyde resin, 0.8 gram of Silquest A1000 was added to the batch.Fifteen seconds after the addition of the phenol formaldehyde resin,7.42 grams of 40% hexamine solution was added to crosslink and cure thephenol formaldehyde resin and was allowed to mix for 1 minute 15seconds. Finally, 1.2 grams of Chembetaine™ CAS, was added and allowedto mix for 1 minute 30 seconds. After the coating procedure, the thirdproppant batch included 3.5% by weight of the polymeric coating. Theapparent specific gravity for this third batch product was 2.05 g/cc.

Example 4

One 750 gram batch (fourth batch) of 30/50 CARBO UltraLite was treatedwith BYK LPD 22287 and then coated with a permeable phenolic coating ina two-step process as described below. The fourth batch of proppant washeated in an oven set to 482° F. (250° C.) for approximately one hour.The heated fourth batch of proppant was then removed from the oven andallowed to cool until it reached a temperature of between 450-460° F. asmonitored by a thermocouple. Once the fourth proppant batch reached thedesired temperature, 7.5 grams of BYK LPD 22287 was added to the batchand allowed to coat the inner channels of the porous substrate for 20seconds, such that the BYK LPD 22287 constituted 1% by weight of thetreated proppant. After the proppant particulates were treated with theBYK LPD 22287 chemical, the batch was coated with a permeable phenoliccoating.

The treated fourth batch of proppant was coated in a two-step processaccording to the following procedure with Plenco 14941. 30 seconds afterthe proppant batch was treated with the hydrophobic chemical and allowedto mix with the proppant substrate in the bowl, 15.2 grams of the phenolformaldehyde resin was added to the treated proppant and allowed to meltand spread over the proppant. Ten seconds after the first addition ofthe phenol formaldehyde resin, 0.8 gram of Silquest A1000 was added tothe batch. Twenty seconds after the first addition of the phenolformaldehyde resin, 4.94 grams of 40% hexamine solution was added tocrosslink and cure the phenol formaldehyde resin and was allowed to mixfor 20 seconds. A second addition of phenol formaldehyde was added tothe batch 30 seconds after the first addition of the phenol formaldehyderesin at an amount of 7.61 grams. Ten seconds after the second additionof the phenol formaldehyde resin, 2.47 grams of 40% hexamine solutionwas added to crosslink and cure the remaining phenol formaldehyde resinand was allowed to mix for 1 minute 50 seconds. Finally, 1.2 grams ofChembetaine™ CAS was added and allowed to mix for 30 seconds. After thecoating procedure, the fourth proppant batch included 3.5% by weight ofthe polymeric coating. The apparent specific gravity for this fourthbatch product was 1.98 g/cc.

Table 1 below shows a comparison of process routes and final apparentspecific gravities (ASG) obtained with each process.

BYK-22287 Resin Process Route Infusion (wt %) Coat (wt %) Final ASG(g/cc) Example 1 NIL 2.0 2.52 Example 2 NIL 3.5 2.38 Example 3 1 3.52.05 Example 4 1 3.5 1.98

Example 5

Batches 1A-D and 2A-D of 30/50 CARBO UltraLite were first treated withvarious amounts of BYK LPD 22287 chemical and then coated with variousamounts of phenol-formaldehyde resin coating (Plenco 14941) using theone-step process disclosed in Examples 1-3 above. In particular, Batch1A was a first sample of 30/50 CARBO UltraLite treated with an amount ofBYK LPD 22287 chemical that resulted in a BYK LPD 22287 concentration of0.25 wt %. Batch 1B was a second sample of 30/50 CARBO UltraLite treatedwith an amount of BYK LPD 22287 chemical that resulted in a BYK LPD22287 concentration of 0.5 wt %. Batch 1C was a third sample of 30/50CARBO UltraLite treated with an amount of BYK LPD 22287 chemical thatresulted in a BYK LPD 22287 concentration of 0.75 wt %. Batch 1D was afourth sample of 30/50 CARBO UltraLite treated with an amount of BYK LPD22287 chemical that resulted in a BYK LPD 22287 concentration of 1.0 wt%. Batches 1A-D were then coated with a phenol-formaldehyde resincoating (Plenco 14941) using the one-step process disclosed in Example 1above to provide lightweight proppant samples, each sample having aphenol-formaldehyde resin concentration of 2.0 wt %.

Batch 2A was a fifth sample of 30/50 CARBO UltraLite treated with anamount of BYK LPD 22287 chemical that resulted in a BYK LPD 22287concentration of 0.25 wt %. Batch 2B was a sixth sample of 30/50 CARBOUltraLite treated with an amount of BYK LPD 22287 chemical that resultedin a BYK LPD 22287 concentration of 0.5 wt %. Batch 2C was a seventhsample of 30/50 CARBO UltraLite treated with an amount of BYK LPD 22287chemical that resulted in a BYK LPD 22287 concentration of 0.75 wt %.Batch 2D was an eighth sample of 30/50 CARBO UltraLite treated with anamount of BYK LPD 22287 chemical that resulted in a BYK LPD 22287concentration of 1.0 wt %. Batches 2A-D were then coated with aphenol-formaldehyde resin coating (Plenco 14941) using the one-stepprocess disclosed in Examples 2-3 above to provide lightweight proppantsamples, each sample having a phenol-formaldehyde resin concentration of3.5 wt %.

The Batches 1A-D and 2A-D, the first batch of Example 1 and the secondbatch of Example 2 were each submerged in water under atmosphericconditions to determine the apparent specific gravity of each sample.The results of this test are depicted in Table 1 below.

TABLE 1 Siloxane Apparent Concentration Specific Batch No. (wt %)Gravity (g/cc) 1 (2.0 wt % Resin Coat) Control-1 0 2.52 1A 0.25 2.018 1B0.5 1.989 1C 0.75 2.024 1D 1 2.011 2 (3.5 wt % Resin Coat) Control-2 02.38 2A 0.25 1.991 2B 0.5 1.982 2C 0.75 1.975 2D 1 2.008

The Batches 1A-D and 2A-D were then submerged in water and placed apressure cell where the pressure upon the batches was increased to 2,000psi for 4 minutes to determine if the proppant would allow water influxunder pressure by measuring the apparent specific gravity of each sampleunder pressure. The results of this test are depicted in Table 2 below.Since no significant change in apparent specific gravity was observed,the results indicated that the application of 2,000 psi did not producea significant influx of water into the porous ceramic proppant.

TABLE 2 Siloxane Apparent Concentration Specific Batch No. (wt %)Gravity (g/cc) 1 (2.0 wt % Resin Coat) 1A 0.25 1.945 1B 0.5 1.940 1C0.75 2.384 1D 1 1.893 2 (3.5 wt % Resin Coat) 2A 0.25 2.150 2B 0.5 1.9802C 0.75 1.891 2D 1 1.995

The foregoing description and embodiments are intended to illustrate theinvention without limiting it thereby. It will be understood thatvarious modifications can be made in the invention without departingfrom the spirit or scope thereof.

What is claimed is:
 1. A lightweight proppant particle, comprising: aproppant particle having an apparent specific gravity of at least about1.5 g/cc; a coating of a hydrophobic material formed on an outer surfaceof the proppant particle; and a coating of an amphiphilic materialformed on an outer surface of the coating of the hydrophobic material.2. The lightweight proppant particle of claim 1, wherein the coating ofthe amphiphilic material has a thickness of at least 10 nm and ispermeable to air.
 3. The lightweight proppant particle of claim 1,further comprising an apparent specific gravity of less than 2.5 g/cc.4. The lightweight proppant particle of claim 1, wherein the proppantparticle has an internal interconnected porosity from about 1% to about75%.
 5. The lightweight proppant particle of claim 4, wherein thecoating of the hydrophobic material is formed on pore walls of theinternal interconnected porosity.
 6. The lightweight proppant particleof claim 1, wherein the hydrophobic material is selected from the groupconsisting of silanes, siloxanes, fluorinated organic compounds, linseedoil, soybean oil, corn oil, cottonseed oil, vegetable oil, canola oil,hydrocarbons, and paraffin and any combination thereof.
 7. Thelightweight proppant particle of claim 1, wherein the amphiphilicmaterial comprises a phenolic resin, an epoxy resin, or a wetting agent.8. The lightweight proppant particle of claim 1, wherein the proppantparticle has a size from about 10 mesh to about 120 mesh.
 9. Thelightweight proppant particle of claim 1, wherein the proppant particleis selected from the group consisting of ceramic proppant, sand, plasticbeads and glass beads.
 10. The lightweight proppant particle of claim 1,wherein an outer surface of the lightweight proppant particle has awater wettability value as measured by a water droplet contact angle ofless than 90° and an oil wettability value as measured by an oil dropletcontact angle of less than 90°.
 11. The lightweight proppant particle ofclaim 1, wherein the lightweight proppant particle has an apparentspecific gravity less than the apparent specific gravity of the proppantparticle.
 12. The lightweight proppant particle of claim 11, wherein theapparent specific gravity of the lightweight proppant is less than 85%of the apparent specific gravity of the proppant particle.
 13. Alightweight proppant pack, comprising: a plurality of lightweightproppant particles, each lightweight proppant particle of the pluralityof lightweight proppant particles comprising: a proppant particle havingan apparent specific gravity of at least about 1.5 g/cc; a coating of ahydrophobic material formed on an outer surface of the proppantparticle; and a coating of an amphiphilic material formed on an outersurface of the coating of the hydrophobic material, wherein thelightweight proppant particle has an apparent specific gravity less thanthe apparent specific gravity of the proppant particle.
 14. Thelightweight proppant pack of claim 13, wherein each lightweight proppantparticle of the plurality of lightweight proppant particles comprises anapparent specific gravity of less than 2.5 g/cc.
 15. The lightweightproppant pack of claim 13, wherein the hydrophobic material is selectedfrom the group consisting of silanes, siloxanes,polytetrafluoroethylene, fluorinated organic compounds, linseed oil,soybean oil, corn oil, cottonseed oil, vegetable oil, canola oil,hydrocarbons, and paraffin and any combination thereof and theamphiphilic material comprises a phenolic resin.
 16. The lightweightproppant pack of claim 13, wherein the proppant particle has an internalinterconnected porosity from about 1% to about 75% and wherein thecoating of the hydrophobic material is formed on pore walls of theinternal interconnected porosity.
 17. A method of fracturing asubterranean formation, comprising: injecting a hydraulic fluid into awellbore extending into the subterranean formation at a rate andpressure sufficient to open a fracture therein; injecting a plurality oflightweight proppant particles into the fracture, each lightweightproppant particle of the plurality of lightweight proppant particlescomprising: a proppant particle having an apparent specific gravity ofat least about 1.5 g/cc; a coating of a hydrophobic material formed onan outer surface of the proppant particle; and a coating of anamphiphilic material formed on an outer surface of the coating of thehydrophobic material, wherein the lightweight proppant particle has anapparent specific gravity less than the apparent specific gravity of theproppant particle; and forming a proppant pack of the plurality oflightweight particles inside the fracture.
 18. The method of claim 17,wherein each lightweight proppant particle of the plurality oflightweight proppant particles comprises an apparent specific gravity ofless than 2.5 g/cc.
 19. The method of claim 17, wherein the hydrophobicmaterial is selected from the group consisting of silanes, siloxanes,polytetrafluoroethylene, fluorinated organic compounds, linseed oil,soybean oil, corn oil, cottonseed oil, vegetable oil, canola oil,hydrocarbons, and paraffin and any combination thereof and theamphiphilic material comprises a phenolic resin.
 20. The method of claim17, wherein the proppant particle has an internal interconnectedporosity from about 1% to about 75% and wherein the coating of thehydrophobic material is formed on pore walls of the internalinterconnected porosity.